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(No Mudel.) 2 Sheets-8heet 1.

. H. P. DAVIS. METHOD OF AND MEANS FOR CONTROLLING ELECTRIC MOTORS.

No. 582,115. Patented May 4,1897.

W/TNESSES: 1 R. CYLZM/ZQM M 7" BY A TOR/V5 Y3,

(No Model.) 2 Sheets-Sheet 2.

H. P. DAVIS.

METHOD OF AND MEANS FOR CONTROLLING ELECTRIC MOTORS.

No. 582,115. Patented May 4,1897.

WITNESSES: INVENTOH Y W, w

14 ORNEYS- UNITED STATES PATENT @rricn,

HARRY P. DAVIS, GF PI'FSISUR l, PENNSYLVANIA, ASSIGNOR TO TIIEIVESTINGI'IOUSE ELEC'IRIC AND IllANI FACTI RING COMPANY, OF

SAME PLACE.

METHOD OF AND MEANS FGR CONTROLLING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 582,115, dated May 4:,1897.

Application filed January 14, 1895. Serial No. 584,832. (No model.)

To LtZZ whom it may concern.-

Be it known that I, HARRY P. DAVIS, a citizen ofthe United States,residing in Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Methods ofand Means for Controlling Electric Motors, (Case No. 620,) of which thefollowing; is a specification.

My invention relates to methods of and means for controlling electricmotors, and more particularly to motors employed for the propulsion ofrailway-vehicles; and it has for its object to provide such method andmeans which shall be simple and effective, and which will serve toproduce desired changes in speed quickly but gradually, and to prevent,as far as possible, injury to the contacts due to the formation of arcsduring changes from one combination or connection to another.

In the drawings, Figure l is a front elevation of a controller made inaccordance with my invention, the cover and wiring being re moved andthe upper portion of the frame and the reversing-switch being shown insection. Fig. 2 is a diagram of the development of the controller-drum,showing also the stationary contacts and the connections of the motorsand rheostats therewith. Fig. 8 is a diagram illustrating the connectionof the motors and resistances in the various relations and positionswhich they assume during a single rotation of the controller-drum.

Referring to the drawings in detail, 1 is the base or frame of thecontroller-stand, and 2 are bearings supported thereby in which isjournaled a shaft 3, which is operated by means of a crank and handle inthe usual manner.

4t is the controller drum or cylinder, which carries at one end anotched disk 5, with which engages a spring-pressed pawl O.

Stationary contacts 7 to 17 are mounted alongside the controller-drumand are bolted to the core or pole 36 of a magnetizing-coil 37. Thesecontacts bear upon a series of contact strips or plates 18 to 35,carried by the controller-drum.

The parts above described are in all respects like those described andclaimed in my application filed January 14, 1895, Serial No.

53l,831, and no claim is made specifically thereto in this application.

The movable contacts 38 of the reversingswitch are carried by a sleeve39, surrounding the upper portion of the shaft 3, and these contacts engage with the stationary contacts 40 and are actuated by a handle 41,rigid with the sleeve 39.

Referring now more particularly to Figs. 2 and 3 of the drawings, M andM represent the motors which are to be controlled, and R,

It and Pa the resistances. The various positions of the controller-drumwith reference to the stationary contacts 7 to 17 are represented byletters (I, I), 0, (Z, c,f, and g.

It will be seen that in the position a of the controller the circuitwill be through contacts 7, 18, 10, and 8, resistances R and It,contacts 10 and 1]., motor M, resistance R contacts 16, a5, 33, 1t, 12,31, 32, and 13, and motor M to the groum In this position of thecontroller-drum the minimum amount of current will flow through themotors and the car will therefore be running at its lowest speed.

In position b the resistance R is cut. out, leaving the resistances Rand R in circuit with the two motors in series, thus providing for anadditional flow of current and consequently a higher rate of speed.

In position a all the resistances are cut out. leaving the two motors inseries, in which po sition there is a maximum flow of current for aseries connection and therefore a maximum speed of the car.

In position (I the following changes occur: First, the resistance R isinserted, the motors being still in series; second, the resistance R isadded to the resistance R, the motors remaining in series; third,themotor M is connected in shunt around the resistance R, theresistances It and It remaining in series with the motor M fourth, motorM is cut out and all three resistances are connected in series with themotor N. These changes (designated by (Z) are made very rapidly, therebeing no notches in the disk 5 corresponding to the several positionswhich are comprised under this designation. On account of the rapiditywith which these changes are made two motors being connected inparallel.

the speed of the car will not be materially affected by the reduction ofthe current due to the reinsertion of the resistances and the cuttin outof one of the motors, but the changes specified are important for thereason that in cutting out one of the motors preparatory to making achange from series to parallel connection the current to be interruptedshould e as small as possible in order that there may be a minimumamount of arcing at the terminals.

In position c resistances R and R are in circuit, resistance R being cutout and the In position f resistances R and R are cut out, leaving themotors in parallel and resistance It in circuit.

In position 9 the motors are connected in parallel without externalresistance, this being therefore the position in which the maximumcurrent is taken and the maximum speed secured, the change in speed upto this point being gradual by reason of the change from series toparallel connection and the gradual cutting out of the resistance incircuit.

By the method of control set forth above I am enabled to make thedesired change from series to parallel connection quickly withoutcausing a sudden and violent change in the speed of the car, which isliable to occur if the connections are not properly arranged.

The method also obviates to a considerable degree the formation of arcsat the contacts when they are separated.

I claim as my invention 1. The method of controlling mechanism operatedby two electric motors, comprising the following steps, connecting themotors in series with resistances, cutting out one of the resistances,shunting one of the motors through the resistance previously cut out, atthe same time leaving the other motor and resistances in circuit,cutting out said shunted motor, and finally connecting the motors inparallel, substantially as described.

2. The method of controlling mechanism operated by two electric motorscomprising the following steps, connecting the motors in series withresistances, cutting out the resistances in order to reach a runningposition, and then reinserting a portion of the same, shunting one ofthe motors and then cutting it out, connecting the motors in parallelwithout the resistance previously in shunt, then cutting out all theresistances, substantially as described.

3. The method of controlling mechanism operated by two electric motorscomprising the following steps: connecting the motors in series withresistances, cutting out of part aml then the whole of said resistances,reinserting a part of the resistances, shunting one of the motorsthrough the remainingresistance, cutting said motor out of circuit,connectingthe motors in parallel without the resistance previously inshunt, and finally cutting out all the resistances.

4:. The combination with a base provided with bearings,reversing-switch, stationary contacts, and a magnet core or pole, of ashaft mounted in said bearings and having a controller-drum rigidlymounted thereon, a series of stationary contacts bolted to said core orpole, a coil for magnetizing said core and contacts, a sleeve carryingthe movable reversing-switch contacts and mounted upon thecontroller-drum shaft to turn independently thereof, and a handlerigidly connected to said sleeve, substantially as described.

In testimony whereof I have hereunto subscribed my name this .lOth dayof January, A. D. 1805.

\Vitnesses:

WEsLEY G. CARR, IIUBERT (1. Tunisia.

